The present invention relates to a recombinant plasmid wherein a DNA fragment containing the env gene of adult T cell leukemia virus [referred to as ATLV hereinafter; ATLV is a synonym of human T cell leukemia virus (HTLV)] or a part thereof is incorporated, a microorganism containing the plasmid and a process for producing an antigen polypeptide encoded by the env gene of adult T cell leukemia virus or a part thereof or a fused protein of the peptide and an enzyme such as .beta.-galactosidase using the microorganism.
Adult T cell leukemia virus is a C-type retrovirus isolated from patients with adult T cell leukemia (hereinafter referred to as ATL) [Yoshida, et al.: Proc. Natl. Acad. Sci., USA, 79, 2031-2036 (1982)]. There are numerous reports that ATL patients have a poor prognosis and that efficacious treatment does not exist leading to a 50% mortality rate within 10 months.
In recent years, an antibody which reacts specifically with cultured MT-1 cells derived from ATL has been shown to exist in the serum of ATL patients [Hinuma, et al., Proc. Natl. Acad. Sci., USA, 78, 6476-6480 (1981)]. The existence of this antibody has been confirmed subsequently in most ATL patients and the corresponding antigens are called ATL-associated antigen (hereinafter referred to as ATLA). It has been found that the antibody specific for ATLA (hereinafter referred to as Anti-ATLA antibody) exists in 25% of normal, healthy adults in areas with a high incidence of ATL. It has also been shown that the distribution of cases possessing the anti-ATLA antibody corresponds to the regions with high ATL incidence. Furthermore, it has been shown that ATLA is mainly the virus antigen of this ATLV. The existence of ATLV genome in the peripheral blood lymphocytes of patients has been established. ATLV has also been detected by culturing the lymphocytes of normal people who are positive to anti-ATLA antibody.
There is a very close correlation between ATL and ATLV, and ATLV is considered to be the causative virus of ATL. Though the route by which infection occurs is still unknown, it has been proved that transfusion of blood is one of the routes. As 25% of healthy people in areas with a high incidence of ATL are anti-ATLA antibody positive, the likelihood of their being carriers of ATLV is extremely high, which means that they must be avoided as blood donors for transfusion.
Therefore, detection of the presence of anti-ATLA antibody will enable avoidance of transfusions from the carriers and early ATL detection. At the present time, detection of anti-ATLA antibody is conducted using acetone fixed slides of cultured cells derived from ATL. However, a simpler, faster method of anti-ATLA antibody detection and earlier ATL diagnosis are desirable.
The present inventors have studied about a method for providing one of the ATLA which is useful for diagnosis of ATLV infection, prevention of ATLV infection and treatment of leukemia caused by ATLV in a large amount and at low cost. As the result, it has now been found that an ATLV antigen peptide encoded by the env gene of the ATLV genome or a part thereof, or a fused protein of the peptide and an enzyme such a .beta.-galactosidase can be accumulated in a large amount by culturing a microorganism containing a recombinant DNA which is obtained by incorporating a DNA fragment containing the env gene and a gene coding for the enzyme into a vector DNA using recombinant DNA techniques, and the present invention has been completed.
It has already been reported that one of the products derived from the env gene is a glycosylated protein (gp 62) having a molecular weight of 62,000 [Hattori, et al.: Gann, 74, 790-793 (1983)] and the entire DNA sequence of ATLV was determined by the present inventors [Japanese Patent Application No. 214287/82, Proc. Natl. Acad. Sci., USA, 80, 3618-3622 (1983)].